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Abstract:
This paper presents an experimental study on the effect of strain rate on the compressive behavior of polyamide composites. Contrary to thermoset woven reinforced composites, thermoplastic woven reinforced composites have always received less interest despite its excellent damage and impact resistances. In this context, this work aims to study the behavior of fiber reinforced thermoplastic composites submitted to high strain rate in compression. The tested material is a thermoplastic composite made of armor tissue of equilibrate glass fiber and the matrix is composed of Polyamide 6 (PA6/Glass). The material is prepared with the fibers woven in 0/90 direction. The compressive mechanical response of PA6/Glass composite was determined in the transverse and longitudinal fibers directions at quasi-static and high strain rates. The hydraulic machine and Split Hopkinson Pressure Bar experiments were conducted to determine the dynamic and quasi static compressive deformation and fracture of the PA6/Glass at strain rates from 10^−5 s^−1 to 1 s^−1 and 100 s^−1 to 2500 s^−1, respectively. In this work, the main goals were to determine the strain rate effect on: elastic modulus, failure stress and failure energy as a function of the loading direction. The strain rate sensitivity of the failure stress level and failure energy were observed. In addition, the failure mechanism was characterized by examining the fracture surfaces using the scanning electron microscopy (SEM) method. In quasi-static conditions of loading, the material reached its capacity due to the formation of shear bands, that concerned all three tested compression directions. In dynamics, the failure took place by shearing followed by delamination. In case of dynamic loading in the direction perpendicular to fibers, the observations made by SEM showed that the failure of the composite had a fragile nature.

Keywords:
woven composite, dynamic behaviour, dynamic fracture, Split Hopkinson pressure bar, failure energy, anisotropy, strain rate